Presently, a provider of voice and/or data communications services operates a communications network that serves a large number of geographically diverse sites, such as cities or metropolitan areas across the nation. The customers of such services may include small-to-large business enterprises or personal users of voice/data services. Communications services may span between different sites of a single business enterprise or may include communications between business enterprises in support of a business relationship. Each concentration of customers or sites that are served by a service provider in a city or metropolitan area may be served by a so-called “point of presence” for the service provider.
Customer sites in the vicinity of a point of presence, that are typically within the range of a few miles of the point of presence, may be connected to the point of presence via some form of access circuit. Traditionally, it has been more practical for a service provider to operate one or more points of presences to serve a large number of customers in a metropolitan area rather than to extend the service provider's core network for one or more services to each physical location where customers may reside. Sometimes an access circuit involves routing a coaxial cable or fiber-optic cable between the point of presence and the customers' sites. More often, however, the existing facilities of a local telephone carrier are leased to provide this connectivity. The well-established local telephone facilities provide at least twisted-pair subscriber loop connectivity to virtually every potential customer location in a metropolitan area. In the case of larger business locations and multi-tenant commercial sites, local telephone facilities typically comprise a large quantity of telephone wires or even provide for wideband or broadband access to the sites.
The portion of the communications network that connects to a customer is typically referred to as the access network. Generally, the access network provides localized communications services between a customer and the edge of a core network. The access network includes what many people refer to as “the last mile,” that is, the connectivity from the house or business to the point of presence. This is the most visible part of the network from the consumers' point of view. The core network, on the other hand, is the transport carrier that handles the dynamic routing of the customer's traffic dependent upon routing instructions.
Often times, the access network and the core network are operated by different service providers. In these situations, the boundaries of the network under the control and operations of a single service provider are typically referred to as a service edge. The access network may be a small network comprising elements that perform some degree of aggregation or routing of information and traffic. In many cases, the access network performs switching or routing based upon predetermined parameters, such as service requirements, provisioning data, and the like.
The services required by customers, residential or business, vary greatly in the type of access services, bandwidth, quality of service (QoS), type of legacy equipment, and the like. Types of services typically include access to the Internet, virtual private Internet Protocol, frame relay services, asynchronous transfer mode (ATM) services, broadband services, point-to-point private line services, voice services, and the like. Typically, the access network provides transport, aggregation, grooming, and switching for each of these types of services independently, which in turn requires the access service provider to provision each of these services separately. Each type of service utilizes different interface and framing standards, and in particular, each type of service typically utilizes different sets of protocols. As a result, access networks may be equipped to interface with and evaluate flows for each type of interface for which the switch is expected to route. In an environment in which voice, frame relay, ATM, TDM private line, and Ethernet customers are desired to be supported by a single switch, there is considerable overhead and complexity associated with processing the various types of services. In many cases, this cannot be effectively accomplished via a single switching device, resulting in multiple switches and resultant parallel networks.
To reduce the overhead associated with supporting the various types of services throughout the access network, it would be preferable to aggregate the traffic for transmission on a common transport or virtual connection, such as a pseudowire, VLAN, or the like. However, the use of a virtual access connection between each customer and each type of customer service may result in a large number of virtual access connections. For example, a metro area having 10 layer 2 switches, 1,000 building aggregators per layer 2 switch, 10 customer edges per building aggregator, each customer requiring on average 2 (or more) services requires 200,000 virtual access connections. Therefore, there is a need to provide virtual circuits across an access network that does not place such a burden on the service edge or other network elements.